The present invention relates to communications in an Internet Protocol (IP) network. More particularly, and not by way of limitation, the present invention is directed to a system and method for facilitating an emergency call in an IP network.
IMS emergency services are currently supported via the Emergency-Call Session Control Function (E-CSCF), refer to, which is described in 3GPP TS 24.229, section 5.1.6 as emergency registration and session establishment at IMS level. In other words, non-validated Emergency Calls at the IMS level are allowed.
However, in a pure cellular all-IP 3GPP IMS network, first Attach and PDP Context Activation are required prior to any calls, both of which depend on the availability of a valid SIM card in the mobile and a valid subscription in the home HLR or roaming partner's HLR.
In addition, Attach and PDP Context Activation without a SIM card or valid registration for Emergency Calls is not yet standardized (3GPP R7 or R8; see 3GPP TS 23.167 Annex E). 3GPP standards currently assume that a circuit switched network is available to be used for cellular based calls and therefore does not address how a pure IMS based 3GPP cellular system would satisfy the Emergency Calls requirements, specifically for non-validated access.
It would be advantageous to have a system and method for providing an emergency call connection that overcomes the disadvantages of the prior art. The present invention provides such a system and method.